Carburetor for internal combustion engines



March 19, 1957 E. A. RocKwELL. 2,785,966

CARBURETOR FOR INTERNAL COMBUSTION ENGINES original Filed oct. 2, 1948 l s A 1 :s mi

. imi 1 if die.

United CARBURETOR FOR INTERNAL COMBUSTION ENGINES Edward A. Rockwell, Los Angeles, Calif.

11 Claims. (Cl. 4S-184) My invention relates to improvements in carbureting apparatus used for forming the charge for operation of internal combustion engines of different types, to give a more effective fuel and air charge for the operation of the engine.

This application is a division of my co-pending application upon System of Auxiliary Carburetion for Internal Combustion Engines, Ser. No. 52,518, led October 2, 1948, and now Patent No. 2,650,081.

It is a general object of the invention to provide a carburetor for internal combustion engines having means for automatically controlling the admission of fuel and air to the engine under varying throttle, load and acceleration conditions to obtain more efficient combustion.

A related but more specific object of the invention is to provide a carburetor having means for automatically adjusting the fuel and air mixture and the throttle so that no-load mixtures are leaner and load and acceleration mixtures are enriched for improving combustion in the engine. It is a related object to provide a carburetor for contro-lling the supply of fuel and air to the engine, operative during minimum load periods, as for example during periods when the manifold Vacuum increases and exceeds the idle vacuum, to limit the fuel supplied while admitting air to the engine.

A more specific object of the invention is to provide a carburetor of the type operated by a vacuum having a primary and a `secondary throat, each having a vthrottle valve for controlling the admission of separate charges of air and fuel to the engine, where the primary throttle valve is manually controlled, and the secondary throttle valve is automatically controlled in accordance with load and acceleration conditions of the engine by vacuum derived from the manifold, and where the throttle valves are Ialso connected by a lost motion linkage, so that under certain conditions the secondary throttle valve is coutrolled in accord with movement of the primary throttle valve. A related object is to provide for automatically controlling the secondary throttle Valve by a diaphragm subject to vacuum within the carburetor and ambient pressure from without, and by an effective area on the throttle valve itself subject to a pressure difference across it and acting in opposition to the diaphragm.

A further specific object is to provide a carburetor of this type where the reduction of Vacuum when manually opening the prim-ary throttle determines the point at which the secondary throttle opens to Iadmit additional air and fuel to the engine to that supplied through the primary throat.

Another object is to provide a spring connected to move the secondary throttle valve where the initial spring force when this throttle valve is closed determines the moment of opening of the throttle valve according to a predetermined lessening of the degree of vacuum acting to hold the throttle valve closed.

An object of my invention is to provide a carburetor which will properly provide for distribution of the tes Patent O charge, and wherein a fuel of any desired rating is intermingled with air for providing -any desired octane rating in high or other compression engines, for example those requiring a high octane rating of the fuel during load conditions, in the operation of the engine.

A further object is to provide a control and throttle arrangement for the carburetor which is effective to conserve the use of the fuel to susbtantially accord with the octane requirements of the engine throughout the throttle and load range of the engine.

A further object of my invention is in an apparatus to effectively utilize liquid petroleum gas, such as butane and/or propane and to provide an apparatus which will feed the liquid petroleum gas vapors to the air stream at a predetermined slight pressure above the atmosphere so as to maintain a desired ratio of air to gas vapor throughout the throttle range of the carburetor and whereby the liquid petroleum gas will be shut olf when the throttle is closed.

A further object is to provide a counterbalanced throttle arrangement for the carburetor which will remain closed at high levels of vacuum on the engine side of the throttle and in which the throttle will automatically open in the carburetor at a predetermined low level of intake manifold vacuum but will not open beyond the point determined by the movement of the throttle of another carburetor, when used therewith.

A furher object is to provide a manual control for cutting in and out the carburetor While permitting the operation of another carburetor.

A further object is to provide a device in which the proportion of high octane mixture can be adjusted so as to accommodate the apparatus to the fuels used, as well as an apparatus which is adjustable according to the type of engine, that is to say, engines having different compression ratios so as to effectively receive the proper ratio of fuel by the octane requirement of the particular engine to which the apparatus is applied.

A further object is in the construction and arrangement of the carburetor which can be readily applied to existing engines having standard carburetors.

It is recognized that although premium gasoline on the market of only a few points of octane rating above the regular gasoline is not rated suiciently high for the requirements of the eicient proposed new internal combustion engines, and also it is a recognized fact that these new engines, as well as the majority of engines in motor cars, require a premium grade of gasoline only during a small percentage of the average operating mileage due to the fact that engines are operated under part throttle most of the time or at a reduced compression. Therefore, the octane rating requirement for operating, for example, up to half throttle is even below the octane rating of the regular grades of gasolines now on the market. However, during acceleration and full load operation, even the premium grades have not suflcient octane rating to give the best results.

It is well known that there may be a shortage of premium grade gasolines, and at the same time, the premium grade gasoline is being wasted by not being utilized by the automobiles in use during perhaps as much as of the time, and, although the use of liquid petroleum gas, such as butane and/or propane have been used in carburetors and combinations of carburetors, it is the ultimate object of my invention to make possible the utilization of only small amounts of the high octane fuels arranged to be carbureted in an auxiliary carburetor arrangement in conjunction with the main carburetor to give the most economical and advantageous results, which should result in a conservation of the available supply of premium gasoline, and particularly for the reason that only a small quantity of the high octane fuel need vbe carried on the vehicle, which in large amounts might not be practical from the standpoint of available storage space on most vehicles.

While it has been proposed to use two different fuels of a high and low octane rating in special carburetors, and I also recognize that butane and/or propane vaporizers and regulators have been in use with various arrangements of adapters to a main carburetor, it is one of the purposes of the invention described and claimed hereinafter to provide a carburetor that can be supplied as an attachment to existing carburetors so that two fuels can be effectively utilized together at the same time in the adjusted desired proportions, resulting in both economy and maximum full load performance, and in the improved and practical arrangement to throw out of action the attached carburetor by a simple apparatus and to maintain this carburetor out of action at times when, vforexample, the fuel feed of the carburetor has been exhausted so that Vthe other carburetor can be operated effectively.

While my .invention is capable of embodiment in many different forms, for example, it is evident that in place of the liquid Apetroleum high octane vapor gas supplied to the carburetor, any arrangement for feeding liquid 4fuel to thejet would be within Athe spirit of my invention. For the purpose of illustration, I have chosen only one vforrn illustrated in the accompanying drawing- The drawing, which is a vertical section through the same, .shows a main carburetor comprising a casing 1,

which has the usual jet 2, float bowl 2a and the connection 2b, which receives fuel from a pump 2c and reservoir 2d for gasoline in the usual manner, venturi tubing 3, choke 4, air cleaner 5, throttle valve 6, having a control lever 7, with the usual full throttle stop 8, and the usual clevis and throttle connections 9 to the accelerator pedal (not shown) `and connected to the throttle clevis pin 10. The carburetor body has the usual flange 11, which, however, is connected to the intake manifold 12 of an internal combustion engine 12a, through an interposed annular ange member 13, having a bore 14, mating with the bore of the carburetor body 1, and having a lateral extending passageway 15 therein, having an annular nozzle 15a, formed by the skirt 15b, and this interposed member forming an adjacent auxiliary carburetor body 16, and having a flange 17 for mating with the air and fuel body casting 18, these castings 16 and 18 supporting within their bores a Venturi tube 19. There is a fuel jet 20 screw threaded into the casting 18. A passage -21 is formed inthe upper part of casting 18, in which there is a screw plug 22 provided with a fuel adjusting jet control screw 23, having a lock nut 24. An air inlet passage 25 is provided in the body casting 18, having an extension 26, leading into the air cleaner 5. Screw threaded into the body casting 18 is a pressure regulator 27, which comprises a regulating diaphragm 28 of flexible material, clamped between the mating flanges of a cover portion 29 Aand the regulator 27 with screws 30. A balance tube 29a is connected to the cover plate and tothe air 4inlet port 25. Adjustably threaded into the :cover 29 is a spring retaining cup 31, having a lock nut 32 and a pressure regulating spring 33, the lower end of which bears on `the diaphragm plate 34, which is fastened to the diaphragm by a similar plate 35 and held together by the valve stem 36. An annular fuel passage 37 is formed in the extension of a bore 38, which has a counterbalancing piston 39 for the rubber valve 40, which valve also has a pasa'geway 4:1 through the same to permit the extension of the valve stem 36, thereby disposed within the passage with a small supply valve 42 attached to said stem. In the floating counterbalancing piston 39 there is a small passageway 43, a suitable inlet connection leading into the annular passage 37 at 44. The radial valve ports-45 for fadmission of gas to the control chamber 46 permits ,the passage'of vapor from the connection 44 to the `diaphragm control chamber-46. Screw threaded into the bore 38 is a closure plug 47. The dotted line 48, leading from the connection 44 to a connection on the higher octane liquid petroleum gas receptacle 49 has 'nterposed therein a heat exchanger 50 and a pressure regulating reducing valve 51. The body 16 has an auxiliary fuel mixture tube or 'passageway 52, which has sliding therewithin a fuel shutoff stem 53, having at the top portion thereof a tapered resilient shutoff valve head 54. This valve head provides a metered annular opening in the mouth of the mixing tube 52 upon axial movemeut in a direction away yfrom said mouth, for the control of the mixture of air and fuel supplied to the carburetor casing 18. Vane guides 55 are provided on the stem 53 to maintain an axial alignment of the said stem. A stop ring 56 is positioned in very close proximity to the top of the tapered throttle valve 57, having a resilient positive valve seat 58 in the closed position thereof. This throttle member has a suitable `packing ring 59, which permits sliding of the stem through the bore in the throttle. A spring 60 is of sufiicent strength to hold valve seat S8 tightly closed. The spring 60 bears on the diaphragm plate 61, having a clamping nut 62, sealing tie diaphragm 63 on the stem 53. A diaphragm cover 64, having an atmospheric vent 64a, is held in place by an annular flange with screws 65 threaded into the body and tightly clamping the .diaphragm to the mating face of the body 16. A hub 66, having a screw thread thereon has an adjustable spring tension nut 67 reacting on a control spring v68. Fastened `to the lower end of the stem 53 is a washer 69 retained by a lock washer 69a, which takes the reaction of the spring 68. A lever bracket mounting 76 is also held in place by the screws 65. At the Vlower portion of the bracket, there is provided a fulcrurn for a pin 71 upon which is mounted the control lever 72, having `an arm 73 and a fastening lug 74 for a tension spring 75, the other end of which is fastened to a spring clip 76, held in place by one of the screws 65. In axial alignment with the valve stern 53, there is an adjustable stop screw 77 with its lock nut 78 screw threaded into the arm 73. Disposed to one side of the lever 72 and arm 73 but bearing on the washer 69 in the position shown, there is asecond lever 79, having integral therewith an extension 80 with an adjustable screw threaded stop 8l, which is in alignment with an abutment S2 on the lever 72. The vlever 79 has an arm 83 having a clevis pin connection 84 for a manual control device 85. interposed in the mechanical connection 86a Ais a spring tension member 86, having a spring 87, a stop 8S, the manual control 8S having a notch 89, adapted to register with the ratchet 90. This ratchet is fulcrurnmed to a fixed support 91. There is an adjustable clevis pin and rod 92 connecting the lever 72 with the throttle lever 7, having connections with the lever 72 in anyiof the series of holes 93 in the lever 72.

The operation of the above described .structure is as follows: In the position of kthe parts in the drawing, the auxiliary .carburetor 16, 13, 64 is shown inthe off position by reason of the adjustment of the manual control device 85, which has applied a tension to .the spring t?? by lbeing pulled back manually into the notch 39 se as to effectively compress the spring 87 away from the stop 8S.

Since the tensionof the spring 87 .is greater than the force of the spring 68, "the fuel shutoff stem 53 will tightly shut ott .any pressure of fuel vapors in the nozzle 2t) by the valve head 54. At :the same time, the throttle valve will be tightly shut at 5S and the spring 60 is of sufhcient strength -to counterbalance any vacuum occuring on the engine `side of the throttle at ythe idle position of the throttle in the position shown and the engine idling.

Now, it being assumed that the `engine is in operation and the main carburetor `1 is functioning in its usual manner, the throttle idle position of the valve 57 is adjusted to give the desired opening for idling on the particular engine on which `the apparatus is installed by adjusting the screw 77 attached to the lever arm 73, which is held abuttingly against the fuel shutoff stem 53 by the pullback spring 75. The throttle rod 9 now may be moved throughout the range of the throttle of the main carburetor, even though the lever 72 is connected to the throttle lever 7 by the link 92. This is because the previously described action of the manual control device 85 will maintain the throttle valve and jet closed, and the lever 72 and arm 73 will simply ride away from the abutment of the adjusting screw 77, the return spring 75 bringing the throttle valve 6 back to the stop idle position. It is apparent in this position that the main carburetor simply functions normally in the conventional manner with a full `range of movement of the throttle 6, and, if the main carburetor is installed on an internal combustion engine of the type having a compression ratio requiring -a higher octane rated fuel than is being used in the carburetor, such as when using a regular grade of gasoline, it may be found advantageous to prevent the full opening of the throttle valve 6, and, for this purpose, there is a stop position provided on the lever 79 by the adjusting screw 81, which can be `adjusted to stop the throttle before the throttle lever 7 reaches the stop screw 8 on the main carburetor, which normally permits the full opening of the throttle. ln this way, the driver is apprised of the fact that he has opened the throttle as wide as should be permitted for this high compression engine. However, in some installations, it will not be desired to utilize this stop position, and in that case, the stop will be adjusted sufficiently away from the abutment 82 on the lever 72 to permit the throttle to open completely to the stop position as determined by the set screw 8 on the main carburetor.

The liquid petroleum gas tank 49 is connected to the auxiliary carburetor by the connection 48 to the outlet 44- on the regulator body 27. The liquid petroleum gas, which has, for example, 1GO-octane rating, will flow by its own pressure through a suitable heat exchanger 50 and enter the annular passage 37 and then through the small opening 43 in the balanced piston 39 and through the valve passage 41 in the resilient regulator valve 40, and then through the radial passages 45. The expanded liquid petroleum gas vapor will act on the under side of the diaphragm 28 and urge the valve 42 to close at a pressure determined by the adjustable control spring 33. This spring preferably has a very low rate and is of a value to maintain the gas pressure leading to the jet 20 at a constant pressure very slightly above atmospheric pressure. It will be noticed that there is a balancing tube 29a all-owing atmosphere at the pressure in the filter to act on the top of the diaphragm 28. It is understood that the liquid petroleum gas, for example, is preferably reduced by the regulator valve 51 to a relatively low pressure above atmosphere, that is to say, somewhat below 5 p. s. i. gauge pressure before entering the carburetor regulator 27, 29.

The secondary valve 40 on the regulator is for the purpose of permitting larger flows at full engine demand while at the same time maintaining a constant pressure at the flow deter-mined by the jet 20 opening, as determined by the adjusting screw 23. It is preferable to have a slight pressure head, such as an inch of water pressure on the jet 20 of the auxiliary carburetor 18, for the reason that it is desirable to have an instant flow of gas for acceleration, as well as to provide a compensating head. For example, if it were required to have a sub-atmospheric pressure to operate the regulator valve 27, 29, the mixture of high octane vapor would have the tendency to run rich atthe full opening of the throttle valve 57, whereas by using a slight positive head at the jet 20, the adjusting screw 23 would necessarily be adjusted to restrict the flow of fuel at low velocities of -air through the auxiliary venturi 19, and at high velocities the restriction by the screw 23 would be sufficient to prevent undue enrichment of the mixture. The slight positive head on the -fuel in the jet 20 also has the advantage of starting easily by providing a flow of gas vapor into the intake manifold 12 so as to avoid unnecessary choking of the main mixture from the regular carburetor, which is harmful to the engine and which causes undue oil dilution and wear of the cylinder walls.

If ratchet 90 is pushed out of the way of the notch 89 and .the manual control device is pushed to the right manually, and after the spring device 86 and 87 hits the stop 88, the linkage 86a will be effective to move the lever 79 and lever arm 83 to the on position shown in dotted lines on the drawing, and it will be noticed that in this position the force of the spring 68 normally will open both the jet 20 and the throttle valve 57 in the auxiliary carburetor, only when the throttle is moved to open position. Instantly liquid petroleum gas vapors will ow down into the auxiliary carburetor and past the annular control area around the throttle and through the passage 15 into the annular space 15a and vthen into the manifold 12. In other words, before starting the engine, the operator can push down the accelerator for a few seconds, and in this way the motor will be able to start on liquid petroleum gas vapors which will readily start the engine. As soon as the engine starts, there will be a high vacuum created on the engine side of the throttle, `and since effective area of the diaphragm 63 is greater than the area of the throttle valve 57, the throttle valve 57 will be closed and the liquid petroleum gas shut olf, as well as the throttle valve being maintained tightly seated on the annular resilient seat 58. The tension of the spring 60 is sufficient to hold this Valve seated against the idle vacuum. The size 0f the venturi throat 19 is selected, for example, at the wide open adjusted throttle position of the main carburetor, as indicated in dotted lines in connection with the stop 8 and the :position of the auxiliary carburetor throttle by the link 92 to permit, for example, as much as half, and in some cases more, liquid petroleum mixture of vapor and air as compared to the mixture of gasoline and air from the main carburetor, so that when these two mixtures are intermingled in the intake manifold, there will be an increased average octane rating of fuel mixture charge entering the engine. However, it is desired to conserve as much of the amount of high octane fuel as the octane rating of the gasoline used in the regular carburetor permits, and, for thi-s purpose, my invention provides a means to vary at a predetermined desired proportion of mixture from the auxiliary carburetor to the main carburetor by reason of the contour of the throttle 57 affecting the annular opening thereof and by the holes 93 provided in the lever 72 for connecting the link 92. This serves as Well to obtain more eicient combustion under varying load and acceleration conditions. For example, in the top hole in the movement of the throttle of the main carburetor, the lever 72 will move to a lesser degree in proportion to the main throttle opening than if the connecting link 92 is connected to the bottom hole of the said lever. Since it is contemplated that this apparatus can be readily applied to existing installation-s, this adjustment can be easily made to suit the particular engine and fuel which is to be used. Furthermore, there is an adjustment provided for determining at what point in the intake manifold depression the auxiliary carburetor cuts in. The spring 68 is selected with a suitable rate to permit the adjustment of the same to control at what time, due to manifold vacuum, the throttle valve 57 will commerce to open along with the jet control of the auxiliary carburetor. For example, at a depression of the manifold vacuum of 4 to 3 inches Hg, it will balance the spring 68 by the differential of pressure acting on the effective area of the diaphragm 63. The moment of opening of the throttle valve is thus calibrated by this spring, so that the throttle valve is controlled when opening the main throttle according to a predetermined lessening of the degree Of avancee vacuum acting on the eiective .area .of the Jthrottle Vvalve 58and on'the effective .area of -th'e diaphragm .63. However, it will lbe apparent .that any time .after this .particular vacuum is :reached the throttle valve will not open beyond the position established by the main throttle by reason of the link 92 in its selected adjusted position in the holes of the control lever 72 so .that the minimum required yproportion will be maintained. The adjusting7 nut 67, for example, would be adjusted to increase the tension of the spring 68 -onthe higher compression motors, and it would be adjusted to decrease the tension of the spring on the lower compression 'motors in order to give the higher octane fuel mixture in proper proportion tothe regular carburetor lmixture for the requirement of the particular engine.

It is 'quite evident that a .liquid 'fuel could be pumped into .the regulator with la suitable :jet size selected in the case where a highfoctan'e liquid fuel is used in the place of the liquid petroleum gas. When an automobile is going down a grade or 'decelerating with the throttle closed, a higher vacuum may `be present in the manifold on the engine side of the throttle. Air can pass the auxiliary throttle by reason of 'the spring 60 'being just strong enough to maintain the throttle closed at idle, which may lpermit air but not gas to ow through the auxiliary carburetor into the manifold, which will control the fuel kair mixture supplied to the engine. leaner mixture can thus be obtained during deceleration periods so as to have a more fumeless exhaust. This will have the effect of saving gasoline consumption of the main carburetor under these no load conditions of operation.

The strength of the pullback spring V75 on the lever 73 is suflicient to overcome the value of the spring 68 in any of its adjusted positions, even when the engine isk not running, so that the fuel vapors of the auxiliary carburetor will be maintained shut olf. The air passage 25 can terminate in its own air cleaner, if desired, but since the apparatus is in close proximity to the main air cleaner a suitable opening through the air cleaner is provided to permit the extension of the air opening into the cleaner which already is provided for the main carburetor.

As an illustration of the proportion of the mixture of the high octane fuel to lower octane 'fuel in the main carburetor, it can be assumed, for example, that half may come from the main carburetor and `half from the auxiliary carburetor, it being understood that the actual scale proportions on the drawing could be adjusted to give any desired proportions at -full load open throttle, and if the fuel being `used in the main carburetor had an octane rating of -80 octanefnum'bers, and the fuel mixture distributed from the auxiliary 'carburetor had 100 octane numbers, there would be a total octane rating of the mixture :of 99 for utilization in the engine, which is above the rating of the usual premium fuels available, and, if a premium fuel was used, and with 100-octane rating of the liquid petroleum gas, there would be proportionately higher octane rating `of the combined mixtures. However, from 90 to -95 percent of the time in the average mileage run by motor vehicles, the manifold depression does not average a low enough depression to permit the higher octane fuel to be used except during acceleration and load operation, so that a small supply of the liquid petroleum gas is all -that will be necessary to carry on most vehicles. The heat exchanger 5t) can be of any type, such as for example, from exhaust gases or heated by the cooling water of the engine.

While I have described my invention above in detail, I wish it to be understood that many changes may be made therein without departing from the spirit of the same.

I claim:

l. In a carburetor 'structure for intermingling `fuel and air for utilization in an internal combustion engine comprising a casing member having a mixing tube through the same, an air inlet and fuel jet at one end portion thereof and a vacuum yresponsive throttle valve 'adapted to move in Iaxial alignment with the said tube in the other end thereof so as to provide a metered annular opening in the axial movement thereof for the control of the mixture of air and fuel supplied to said casing member, a fuel inlet controlling stem attached to and carrying thereon slidably the throttle valve, said stem extending to the exterior of the said casing member at the'said other .end thereof for the control thereof and a vacuum responsive diaphragm connected to said stern responsive to said valve controlled vacuum.

2. ina carburetor structure for intermingling fuel and air for utilization in an internal combustion engine comprising, a casing member having a mixing tube through the same, an air inlet and fuel jet Vat one end portion thereof, and a vacuum responsive throttle valve adapted to move in axial alignment with the .said tube inthe other end thereof so as to provide a metered annular opening in the axial movement thereof, for the control of the mixture of air and fuel supplied to the first mentioned end of the said casing member, a fuel inlet controlling stem attached to and .carrying thereon slidably the throttle valve, said stem extending to the exterior of the said casing member for the control thereof, a pressure responsive movable wall arranged between the valve and the exterior of the casing whereby the same acts as a counterbalancing area for the said valve and a spring .biasing means tending to open the said valve by reaction on the casing member.

3. In a carburetor structure for intermingling fuel and air for utilization in an internal combustion engine comprising, a casing member having a mixture tube through the same, an air inlet and fuel jet at one end portion thereof and a vacuum responsive throttle valve adapted to move in axial alignment with the said tube in the other end thereof so as to provide a metered annular opening in the axial movement thereof, for the control of the mixture of air and fuel supplied to the first mentioned end of the said casing member, a fuel inlet controlling stem carrying, slidably thereon, the throttle valve, said stem extending through the throttle valve to the outside of the casing for the control thereof and having a valve adapted to close the fuel jet and a pressure responsive movable wall arranged between the valve and the exterior of the casing, whereby the same acts as a counterbalancing area for the said valve and a spring biasing means tending to open the said valve by reaction on the casing member.

4. In a carburetorstructure for intermingling fuel and air for utilization in an internal combustion engine coinprising, a casing member having a mixing tube through the same, an air inlet and fuel jet at one end portion thereof, a vacuum responsive throttle valve adapted to move in axial alignment with the said tube in the other end thereof so as to provide a metered annular opening in the axial movement thereof, for the control of the mixture of air and fuel supplied to the lirst mentioned end of the said casing member, a fuel inlet controlling stem attached to and carrying thereon slidably the throttle valve `by an interposing spring between the valve and thel stem, said stem extending to the outside of the casing for the control thereof and a pressure responsive movable wall arranged between the vvalve and the exterior of the casing, whereby the same acts as a counterbalancing area for the said valve and a spring biasing means tending to open the said valve by reaction on the casing member.

5. In a carburetor structure for intermingling fuel and air for utilization in an internalcombustion engine comprising, a casing member having a mixing tube through the same, an air inlet and fuel jet at one end portion thereof and a vacuum responsive throttle valve adapted to move in axial alignment with the said tube in the other end thereof so as to provide a metered annular opening inthe movement thereof, for the control of the mixture of air and fuel supplied to the first mentioned end of the said casing member, a throttle lever, a fuel inlet controlling stem attached to and carrying thereon slidably the throttle valve, said stem extending to the exterior of the said casing member and having an operative connection with the lever, a bracket for supporting the fulcrum of the lever for the operation thereof, a vacuum resonsive diaphragm connected to said stem responsive to said valve controlled vacuum, a spring biasing means located between the lever and the casing and an additional spring biasing means located between the casing and the stem. 1

6. In combination, in a carburetor for utilization in an internal combustion engine having a down draft mixing tube for air and fuel, a jet at the upper axial end thereof and a vacuum responsive throttle valve at the other axial end thereof, said throttle valve having a fuel inlet controlling stem portion attached thereto and on which said valve is slidably carried, the stem providing a shutoff valve for the jet at the closed position of the throttle, a counterbalancing diaphragm cooperating with said stern and throttle valve and held in sealing relation with the mixing tube at the lower end thereof, and an outlet for the mixture between the diaphragm and the throttle, said stem having an extension extending beyond the mixing tube at the said other axial end thereof for the operation and control thereof.

7. A carburetor of the type operated by a vacuum comprising a casing having therein passageways for the inlet of air and fuel, an outlet passageway for the air and fuel mixture, a throttle valve located between the mixture passageway and the air and fuel passageways, a diaphragm supported in the casing and adapted to communicate on one side to a vacuum within the carburetor and on the other side to ambient pressure exterior of the carburetor, means to control the opening of the throttle valve including an effective area on the throttle valve itself subject to a difference of pressure across the same producing an effective force acting -in one direction, selective manual means for controlling the vacuum including a lever, said means to control the opening of the throttle valve also including a linkage between the lever and the valve having a lost motion, the extent of the movement of the lever by the manual means determining the extent of the lost motion and acting as a limit for the degree of opening of said throttle valve, the said diaphragm having an effective area subject to said pressures and mounted to produce an effective force acting in a direction to affect the movement of the throttle valve in opposition to the effective force acting on said valve by means of a connection between the diaphragm and throttle valve, said diaphragm and throttle valve being adapted to move together when there is an over-balance of the opposed forces between the throttle valve and the diaphragm, spring means acting between the casing and the said connection having an initial force when the throttle valve is closed whereby the moment of opening of the throttle valve is calibrated by said spring to respond to the said means to control the throttle valve according to a predetermined lessening of the degree of vacuum acting at that moment on said effective areas conjointly with the spring to hold the throttle valve closed, which is overbalanced at said moment by the effective force acting to open said valve.

8. A carburetor of the type operated by a vacuum comprising a casing having therein passageways for the inlet of air and fuel, an outlet passageway for the air and fuel mixture, a throttle valve located between the mixture passageway and the air and fuel passageways, a diaphragm supported in the casing and adapted to communicate on one side to a vacuum within the carburetor and on the other side to ambient pressure exterior of the carburetor, means to control the opening of the throttle valve including an effective area on the throttle valve itself subject to a difference of pressure across the same 10 A producing an elective force acting in one direction, selective manual means for controlling the vacuum including a lever, said means to control the opening of the throttle valve also including a linkage between the lever and the valve having a lost motion, the extent of the movement of the lever by the manual means acting as a limit for the degree of opening of said throttle valve, the said diaphragm having an effective area subject to said pressures and mounted to produce an effective force acting in a direction to affect the movement of the throttle valve in opposition to the effective force acting on said valve itself by means of a connection between the diaphragm and throttle valve, said diaphragm and throttle valve being adapted to move together when there is an overbalance of the opposed forces between the throttle valve and the diaphragm, spring means acting between the casing and the said connection having an initial force when the throttle valve is closed whereby the moment of opening of the throttle valve is calibrated by said spring to respond to the said means to control the throttle valve according to a predetermined lessening of the degree of vacuum acting at that moment on said effective areas conjointly with the spring to hold the throttle valve closed, which is over-balanced at said moment by the effective force acting to open said valve, and means effective upon return movement of said lever and, upon taking up the clearance of the lost motion, for positively closing the throttle valve irrespective of said opposed forces acting on said connection.

9. A carburetor for use with an internal combustion engine subject to varying loads, having an air and fuel inlet, a mixture outlet, a throttle valve located between the inlet and outlet, a shut-off valve controlling the fuel inlet, a vacuum responsive diaphragm connected to said throttle valve so as to close the throttle valve upon a predetermined vacuum being reached in said engine at a minimum load, a spring device acting on the diaphragm for opening said fuel valve at a predetermined lowering of the vacuum commensurate with a predetermined increased load, said throttle valve having a connection to said diaphragm and said shut-off fuel valve, said connection including a second spring device for permitting the opening of the throttle valve at said minimum load while maintaining the shut-olf fuel valve shut by the diaphragm, said throttle valve having a pressure responsive area thereon which is less than the effective area of the said diaphragm to produce a force to counterbalance said second spring at said minimum load so that air will be drawn through to the engine when the shut-off fuel valve is closed.

l0. A carburetor for use with an internal combustion engine subject to varying loads comprising, an air and fuel inlet, a vacuum operated throttle valve for controlling the mixture from said air and fuel inlet, a fuel shutoff valve, a housing therefor having an air passage at one end of the housing on the inlet side of the throttle valve, and a controlled mixture passage at the other end thereof on the opposite side of said throttle valve, said air passage including a venturi containing a fuel jet controlled by a stem on said shut-off valve extending through the throttle valve which has a slidable bearing on said stern provided with a limiting stop adjacent to said throttle valve, a vacuum responsive counterbalancing diaphragm in said housing attached to said stem tending to close said throttle valve upon a reduction of pressure in said controlled mixture passage against the action of the vacuum di rectly acting on the throttle tending to open the throttle valve, a spring on said stem biasing the throttle valve toward closed position, having a greater force than action ordinarily of vacuum directly on the throttle valve, said biasing spring permitting the fuel shut-off valve to close while allowing the throttle valve to open under decrease of load.

1l. A carburetor for use with an internal combustion engine subject to varying loads comprising, an air and fuel inlet, a vacuum operated throttle valve for controlling the `rnxfnlrfe from isaid `,air `and lfuel inlet, a fuelA shut-soif ,valve '1 gifhfef hving'an lair passage a' ofte en'cluofA the,l housing s fn the inlets'ide' of the throttlel yale, and acontrolled lfr'liytlure passageat the otherV Verlfd thereof on A,the opposite sideof's'aid throttle Valve, saidy air passage incldirn'ga VVentliri containing ,a fuel jet controlled by a stem or'risaind shut-'off ialve eritending throghthe throttle valve'which has a slidable bearing on said' stem provided with a limiting stop adjacent to said throttle Valve, a vacunrn responsive counterb'alancing diaphragm insaid housing y attached tousaid stern Vtendirlgto close said'throttle valve v upon a redction lof bresfs'nre in Vsaid controlled mixturepassage against the action of the Vacuum directly actingrori thethrottle tending to open the'throttle valve,

a spring vozn said stem biasing thetlirottlelX/ al've toward 15 2,027,492

1,218,545 Giddens Mar. r6, 1917 1,743,127 Fuller Ian. 14, 1930 1,802,321 Malzleet'".al'." `i `l ADL'ZI, 1931 SnodgrassV Q Jari. V121, '.1936

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9. A CARBURETOR FOR USE WITH AN INTERNAL COMBUSTION ENGINE SUBJECT TO VARYING LOADS, HAVING AN AIR AND FUEL INLET, A MIXTURE OUTLET, A THROTTLE VALVE LOCATED BETWEEN THE INLET AND OUTLET, A SHUT-OFF VALVE CONTROLLING THE FUEL INLET, A VACUUM RESPONSIVE DIAPHRAGM CONNECTED TO SAID THROTTLE VALVE SO AS TO CLOSE THE THROTTLE VALVE UPON A PREDETERMINED VACUUM BEING REACHED IN SAID ENGINE AT A MINIMUM LOAD, A SPRING DEVICE ACTING ON THE DIAPHRAGM FOR OPENING SAID FUEL VALVE AT A PREDETERMINED LOWERING OF THE VACUUM COMMENSURATE WITH A PREDETERMINED INCREASED LOAD, SAID THROTTLE VALVE HAVING A CONNECTION TO SAID DIAPHRAGM AND SAID SHUT-OFF FUEL VALVE, SAID CONNECTION INCLUDING A SECOND SPRING DEVICE FOR PERMITTING THE OPENING OF THE THROTTLE VALVE AT SAID MINIMUM LOAD WHILE MAINTAINING THE SHUTT-OFF FUEL VALVE SHUT BY THE DIAPHRAGM, SAID THROTTLE VALVE HAVING A PRESSSUR RESPONSIVE AREA THEREON WHICH IS LESS THAN THE EFFECTIVE AREA OF THE SAID DIAPHRAGM TO PRODUCE A FORCE TO COUNTERBALACE SAID SECOND SPRING AT SAID MINIMUM LOAD SO THAT AIR WILL BE DRAWN THROUGH TO THE ENGINE WHEN THE SHUT-OFF FUEL VALVE IS CLOSED. 